Vaccines
Figure 4: Profile of Meningococcal Disease by Serogroup in England and Wales Between 1998/1999 and 2009/2010 (provisional data)
100 120 140
20 40 60 80
0
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Epidemiological years
W135 cases Total incidence X cases B incidence Y cases C incidence
Evidence of indirect protection also comes from infants three months of age and under, who are too young to be fully protected by immunisation. Cases of serogroup C disease in these young infants fell after 2000–2001 from 13 cases to zero or one case every year31 seven-year period).
to one in 2007–2008 (provisional data from the Health Protection Agency).34
meningococci.40
In multicentre surveys of 15–19-year-old students eligible for immunisation in 1999, 2000 and 2001, a large decrease in the prevalence of carriage of serogroup C meningococci and carriage of serogroup C organisms that contained the gene responsible for C capsule production was found between 1999 and 2001 based on over 48,000 samples with 8,599 meningococci isolates. The effect of vaccination on reducing carriage of the highly virulent serogroup C ST-11 strain was particularly marked. Vaccine effectiveness against carriage of serogroup C meningococci in this study population was estimated to be 75 % (95 % confidence interval [CI] 23–92 %) and lasted for at least two years. This reduction in carriage is consistent with a reduction in transmission and a herd immunity effect and, combined with direct vaccine protection against disease, has been key to the marked impact on serogroup C disease since the MenC vaccine was introduced.
Protection against carriage and population herd immunity effect, largely induced by expansive catch-up campaigns, is considered the major determinant of programme outcome and cost-effectiveness.41
However,
the duration of herd immunity is not known and, while a key factor for consideration is the duration of protection against carriage conferred on vaccinees, there are as yet no established correlates of protection. Mathematical modelling in England and Wales suggests that the indirect effects of the catch-up campaign are likely to persist for several more years.33
Serogroup C Meningococcal Conjugate Vaccine Effectiveness
between 2003–2004 and 2009–2010 (four over the
The Netherlands introduced routine MenC immunisation at 14 months of age in September 2002, with the catch-up campaign for children one to 18 years of age conducted the same year. Cases in The Netherlands fell by 94 % between 2001 and 2004, from 276 to 17.24
This decrease included a fall in infants under one year of age from 20 cases to one case in the same period. There have been no reported vaccine failures in The Netherlands up to August 2010.35 These findings are consistent with data from England and Wales indicating that a single dose in the second year of life affords high levels of protection. However, the absence of vaccine failures could also be explained by the high levels of herd immunity conferred by the large catch-up campaign that achieved very high coverage.
Australia also introduced a single dose, early in 2003, at 12 months of age, with a catch-up to 20 years of age. The impact was more difficult to assess as disease incidence was already falling before the introduction of the vaccine, but in New South Wales the number of cases fell from 213 in 2002 to 50 in 2005: a reduction of over 75 %.36
A MenC vaccine was launched in the Republic of Ireland at the beginning of October 2000 for everyone under 23 years of age.37
The incidence
of group C disease fell dramatically from 132 cases (3.6 per 100,000) in 199938
to four cases in 2006 (0.1 per 100,000): a 97 % reduction.39
Nasopharyngeal Carriage of Neisseiria meningitidis The importance of the impact of the MenC vaccine on carriage of N. meningitidis in the nasopharynx was not fully recognised at the time the vaccine was introduced. MenC immunisation has subsequently been shown to significantly reduce carriage of serogroup C
132
Initial estimates of the effectiveness of the three-dose MenC infant programme in England to the end of March 2004 were high up to one year after immunisation at 93 % (95 % CI 67–99 %).42
However,
effectiveness fell significantly from one year after the last scheduled dose. The most recent estimates of vaccine effectiveness (to the end of June 2009) also found high effectiveness (97 % [95 % CI 91–99 %] within one year of primary immunisation, which then fell to 68 % (95 % CI –63 to 90 %) one year or more after completion of the primary schedule; this decline was statistically significant (p<0.001).33
There was
also evidence of a more gradual decline over a longer period, but this observation was based on very small numbers of cases, with vaccine effectiveness estimated at 31 % (95 % CI –2,800 to –90 %) three years or more after routine infant immunisation. Effectiveness was calculated at between 83 and 97 % in all other cohorts and no statistically significant fall with time since immunisation was found. This pattern is consistent with the observation that serum bactericidal activity titres decline more rapidly in individuals immunised at a younger age than in those who received the MenC vaccine when they were one year of age or older.43
A similar decline in effectiveness was demonstrated for infants immunised under the two-, four-, six-month schedule in Spain. Vaccine effectiveness fell from 98.4 % (95 % CI 95.7–99.4) within one year from vaccination to 78.0 % (95 % CI 3.1–95.0) after one year following vaccination.44
A number of countries have reduced the number of infant doses administered and included a booster dose of a MenC-containing vaccine, with the expectation that elevated protection would then persist through to adolescence. However, antibody persistence following boosting in the second year of life was shown to be similar to that following the primary meningococcal C conjugate (MCC) vaccination schedule.45
Two years after the booster, the percentage EUROPEAN INFECTIOUS DISEASE
Total cases
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